1. Field of the Invention
This invention relates to a durable press process for cellulosic fiber-containing fabrics and more particularly to a process which utilizes formaldehyde and a non-gaseous catalyst to impart wrinkle resistance to cellulosic fiber-containing fabrics.
There have been a great many proposed processes in recent years for treating cellulosic fiber-containing products, such as cloth made of cotton or cotton blends, with formaldehyde to provide durable cross-linking of the cellulose molecules and to thereby impart durable crease resistance and smooth drying characteristics to the goods. However, problems have been encountered, and although a number of the processes have been operated commercially there is a great need for improvement.
As pointed out in U.S. Pat. No. 3,706,526, granted Dec. 19, 1972, the processes have tended to lack reproducibility, since control of the formaldehyde cross-linking reaction has been difficult. The process of this patent is said to solve the control problem by controlling moisture present in the cellulosic material during the reaction. The cellulosic material is conditioned to give it a moisture content of between about 4 to 20 percent, preferably 5 to 12 percent, based on the dry weight of the cellulose fiber, and it is then introduced into a gaseous atmosphere containing water vapor, a cellulose cross-linking amount of formaldehyde (e.g. 15 to 60 volume percent) and a catalytic amount of sulfur dioxide. However, the moisture control is difficult and the use of a toxic gas as the catalyst presents a safety factor as well as additional expense for environmental protection by requiring scrubbers and the like to eliminate the toxic substance from any effluent. Also, the presence of the gaseous catalyst and steam result in corrosion of the curing chamber.
Canadian Pat. No. 897,363, granted Apr. 11, 1972, discloses a process for the formaldehyde cure of cellulosic fibers which comprises applying to the cellolosic material, a solution of zinc chloride, ammonium chloride, phosphoric acid or zinc nitrate, conditioning the fabric to a moisture content of between about 7 and 15 based on the dry weight of the fabric, and thereafter exposing the catalyst-containing fabric or article made therefrom to an atmosphere of formaldehyde or formaldehyde vapor (5 to 75 percent volume percent) at a temperature between about 90.degree. and 150.degree.C.
The process requires precise moisture control and is said to be limited to the use of the few select catalysts.
Accordingly, a need exists for a simple and economical durable press process which does not depend on precise moisture control to moderate the cross-linking, does not require high concentrations of formaldehyde or utilize a noxious gaseous catalyst.